Bitcoin is really bad for using as currency, due to the fact that there is a permanent, public ledger of all transactions. Why would you want anyone you pay to be able to see and trace every transaction you've ever made? Pay rent in bitcoin, now your landlord can calculate your spending and who you do transactions with. And yes, there are services that aggregate and obfuscate transactions in order to make them less traceable, but now you've just reinvented the same centralized payment processor system that the whole thing is supposed to be replacing... so... what's the point?
Cash is good for using as currency.